The present invention relates to an apparatus for charging a battery with a self-exciting generator and, more particularly, to an apparatus for charging a battery of a motor vehicle with a self-exciting generator having a more efficient pre-excitation of the self-exciting generator.
A known apparatus for charging a battery, particularly in a motor vehicle driven by an internal combustion engine, comprises a self-exciting generator having an exciting winding through which an exciting current can pass and a generator output, a regulator connected in series to the exciting winding of the generator for regulating the exciting current in the exciting winding; a starter arrangement including a starter motor for starting the internal combustion engine and a starter relay including a starter relay coil and a starter relay switch for switching on the starter motor; a battery having two terminals, one of the terminals being connected to ground together with the generator output and the other of the terminals being connected to a supply line; and an ignition/starter switch connected to the supply line, the ignition/starter switch having an initial position, an operating position and a starting position and also an operating contact and a starting contact and the ignition/starter switch being structured and electrically connected with the battery, with consuming devices and with the starter arrangement, so that no current flows through the ignition/starter switch in the initial position of the ignition/starter switch, current flows through the operating contact and the consuming devices when the ignition/starter switch is in the operating position and current flows through the starter arrangement including the starter motor and consuming devices when the ignition/starter switch is in the starting position; and a first current branch including the operating contact of the ignition/starter switch, the first current branch being connected to the exciting winding of the generator.
Generators which energize themselves after the motor driving them is started are used in motor vehicles. This self-excitation must be reliable in such a way that the power supply system can be supplied with power immediately after starting the motor of the generator. The magnetic remanence alone is normally not sufficient for ensuring the self-excitation. Therefore, the attempt is made to promote the self-excitation by various circuits and different levels of power expenditure. One of the customary possibilities for promoting the self-excitation is to use the charge control light simultaneously to pre-excite the generator. For this purpose, energy is supplied to the exciting winding from the battery via the charge control light when starting. In this case, the excitation of the generator is dependent on the charge state of the battery, on the battery voltage, the frequency of starting or attempts at starting, but particularly on the output value and the operativeness of the charge control light, and also on the connection value or wattage of the loads already connected to the generator and on the ambient temperature. Under the most unfavorable circumstances, the generator does not excite itself and the battery is not recharged.
Therefore, in order to improve the self-excitation, it is provided according to DE-OS 26 08 606 to supply the exciting winding with exciting power from the battery via the starter during the starting process by an additional connection via a resistor and a diode. But this possibility of supplying additional exciting power has the disadvantage that it is terminated immediately after the starting process has ended. To the extent that it has not been completely accomplished after the starting process, the excitation of the generator is therefore not effected in the desired manner in order to achieve the required generator output voltage as quickly and as reliably as possible.